Typical strain wave gearing assembly includes three basic components: a wave generator, a flex spline, and a circular spline. The wave generator is made up of two separate parts: an elliptical disk called a wave generator plug and an outer ball bearing. Teeth are positioned radially around the outside of the flex spline. The flex spline fits tightly over the wave generator, so that when the wave generator plug is rotated, the flex spline deforms to the shape of a rotating ellipse and does not slip over the outer elliptical ring of the ball bearing. The circular spline is a rigid circular ring with teeth on the side. The flex spline and wave generator are placed inside the circular spline, meshing the teeth of the flex spline and the circular spline. Because the flex spline is deformed into an elliptical shape, its teeth only actually mesh with the teeth of the circular spline in two regions on opposite sides of the flex spline.
When the wave generator plug rotates, the flex spline teeth which are meshed with those of the circular spline, slowly change position. For every full rotation of the wave generator, the flex spline would be required to rotate a slight amount backward relative to the circular spline. Thus, the rotation action of the wave generator results in a much slower rotation of the flex spline in the opposite direction.
This prior art design has numerous drawbacks associated with the designs. The wave generator plug deforms the bearing in to the shape of an ellipse thereby reducing the life of the bearing.
Accordingly, there remains a need for an improved harmonic drive assembly that will eliminate the aforementioned drawbacks associated with the prior art design.